This invention relates to a synchronizing circuit, and more particularly to a useful synchronizing circuit suitable for application to time division and simultaneous telecommunication system.
A simultaneous telecommunication system capable of simultaneous transmission and reception of aural information between a calling station and a called station has been set forth in the copending application Ser. No. 646,475 filed by Kotzawa et al. on Jan. 5, 1976 and Ser. No. 653,249 filed by Kotezawa et al. on Jan. 28, 1976. In such a simultaneous telecommunication system, it is necessary to attain complete synchronization of signal transmission and reception between a calling station and a called station. An improved synchronizing circuit capable of meeting such requirement is set forth hereat.
In a typical synchronizing system conventionally employed in the art, a synchronizing signal is transmitted together with an information signal from a transmitting station, and in a receiving station, the received synchronizing and information signals are separated by means such as a filter. The synchronizing signal thus separated is used as an input to the electrical circuit of the receiving station. However such conventional synchronizing system has been defective in that a high-quality, high-precision filter must be provided to precisely separate the synchronizing signal from the information signal. Further, the circuitry of the system becomes quite complex due to the necessity for transmission, reception and separation of the information signal and synchronizing signal.